The present invention relates to an athletic shoe midsole design and construction. More particularly, the invention relates to a midsole assembly where there are provided a midsole formed of soft elastic material and a corrugated sheet disposed in the midsole.
The sole of an athletic shoe used in various sports is generally comprised of a midsole and an outsole fitted under the midsole, directly contacting the ground. The midsole is typically formed of soft elastic material in order to ensure adequate cushioning.
Running stability as well as adequate cushioning is required in athletic shoes. There is need to prevent shoes from being deformed excessively in the lateral or transverse direction when contacting the ground.
As shown in Japanese Utility Model Examined Publication No. 61-6804, the applicant of the present invention proposes a midsole assembly having a corrugated sheet therein, which can prevent such an excessive lateral deformation of shoes.
The midsole assembly shown in the above publication incorporates a corrugated sheet in a heel portion of a midsole and it can produce resistant force preventing the heel portion of a midsole from being deformed laterally or transversely when a shoe contacts the ground. Thus, the transverse deformation of the heel portion of a shoe is prevented.
However, it depends on the kind of athletics or athletes whether an athlete lands on the ground more frequently from the medial portion or the lateral portion of the heel at the onset of landing. For example, since tennis or basketball players move more often in the transverse direction and the medial portions of their heels tend to first contact the ground, the heels lean outwardly and so-called supination often occurs. On the other hand, since runners or joggers tend to land on the ground from the lateral portions of their heels and the load moves toward the toes, the heels lean inwardly and so-called pronation often occurs.
These pronation and supination are normal movements when an athlete""s foot comes in contact with the ground. But over-pronation or over-supination may cause damages to the ankle, knee and hip of an athlete.
In the conventional midsole design there is provided a corrugated sheet having a constant wave configuration in both the transverse direction and the longitudinal direction of the heel portion. Therefore, the prior art midsole has a constant compressive hardness throughout the midsole and as a result, it cannot control effectively pronation and supination of the foot of an athlete although controlling them is required according to the kind of athletics.
Generally, by inserting a corrugated sheet the heel portion of a midsole tends to be less deformed in the transverse direction. When the corrugated sheet is formed from high elastic material the heel portion of a midsole tends to be less deformed in the vertical direction as well. Therefore, when a corrugated sheet has a constant wave configuration the heel portion of a midsole where adequate cushioning is required may show less cushioning properties in contacting the ground.
On the other hand, good cushioning is indispensable requirements of athletic shoes but too high cushioning may absorb an athletic power such as propellant or jumping power of an athlete.
The object of the present invention is to provide a midsole assembly for an athletic shoe which can prevent the over-pronation and over-supination in landing by preventing the shoe from being deformed in the transverse direction according to the kind of athletics and can not only ensure adequate cushioning but also prevent an athletic power from being lessened.
The present invention provides a midsole assembly for an athletic shoe and its manufacturing process.
In one embodiment, a midsole assembly comprises a midsole and a corrugated sheet disposed in at least a heel portion of the midsole. The midsole is formed of soft elastic material. Either or both amplitude and wavelength of wave configuration of the corrugated sheet is made different either or both between a front end portion and back end portion, and between a medial portion and lateral portion of the heel portion.
A second embodiment provides a midsole assembly according to the first embodiment, wherein hardness of the corrugated sheet is higher than that of the midsole.
A third embodiment provides a midsole assembly according to the first embodiment, wherein the corrugated sheet is comprised of fiber-reinforced plastic.
A fourth embodiment provides a midsole assembly according to the third embodiment, wherein the fibers of the fiber-reinforced plastic are aligned in one direction.
A fifth embodiment provides a midsole assembly according to the fourth embodiment, wherein the fibers of the fiber-reinforced plastic are oriented to the direction coinciding with the direction of ridges of the wave configuration.
A sixth embodiment provides a midsole assembly according to the fourth embodiment, wherein the fibers of the fiber-reinforced plastic are oriented within xc2x130xc2x0 relative to the direction of ridges of the wave configuration.
A seventh embodiment provides a midsole assembly according to the third embodiment, wherein the fibers of the fiber-reinforced plastic are woven by filling and warp, the modulus of elasticity of the filling being greater than or equal to that of the warp.
An eighth embodiment provides a midsole assembly according to the seventh embodiment, wherein the filling being oriented to the direction coinciding with the direction of ridges of the wave configuration.
A ninth embodiment provides a midsole assembly according to the seventh embodiment, wherein the filling being oriented within xc2x130xc2x0 relative to the direction of ridges of the wave configuration.
A tenth embodiment provides a midsole assembly according to the first embodiment, wherein a plurality of ribs are provided on the surface of the corrugated sheet, the ribs being oriented to the direction coinciding with the direction of ridges of the wave configuration.
An eleventh embodiment provides a midsole assembly according to the first embodiment, wherein the corrugated sheet is comprised of a first corrugated sheet and a second corrugated sheet, the first corrugated sheet being formed of thermoplastic or thermosetting resin, the circumferential end surface thereof being located inside the side surface of the heel portion of a shoe, the second corrugated sheet being formed of soft elastic material having smaller modulus of elasticity than that of the first corrugated sheet, the circumferential end surface thereof being located at substantially the same position as the side surface of the heel portion of a shoe.
In a twelfth embodiment, a midsole assembly comprises a midsole and a corrugated sheet disposed in at least a heel portion of the midsole. The midsole is formed of soft elastic material and has an aperture in the heel central portion. Either or both amplitude and wavelength of wave configuration of the corrugated sheet is made different either or both between a front end portion and back end portion, and between a medial portion and lateral portion of the heel portion.
A thirteenth embodiment provides a midsole assembly according to the twelfth embodiment, wherein hardness of the corrugated sheet is higher than that of the midsole.
A fourteenth embodiment provides a midsole assembly according to the twelfth embodiment, wherein the corrugated sheet is comprised of fiber-reinforced plastic.
A fifteenth embodiment provides a midsole assembly according to the fourteenth embodiment, wherein the fibers of the fiber-reinforced plastic are aligned in one direction.
A sixteenth embodiment provides a midsole assembly according to the fifteenth embodiment, wherein the fibers of the fiber-reinforced plastic are oriented to the direction coinciding with the direction of ridges of the wave configuration.
A seventeenth embodiment provides a midsole assembly according to the fifteenth embodiment, wherein the fibers of the fiber-reinforced plastic are oriented within xc2x130xc2x0 relative to the direction of ridges of the wave configuration.
An eighteenth embodiment provides a midsole assembly according to the fourteenth embodiment, wherein the fibers of the fiber-reinforced plastic are woven by filling and warp, the modulus of elasticity of the filling being greater than or equal to that of the warp.
A nineteenth embodiment provides a midsole assembly according to the eighteenth embodiment, wherein the filling being oriented to the direction coinciding with the direction of ridges of the wave configuration.
A twentieth embodiment provides a midsole assembly according to the eighteenth embodiment, wherein the filling being oriented within xc2x130xc2x0 relative to the direction of ridges of the wave configuration.
A twenty-first embodiment provides a midsole assembly according to the twelfth embodiment, wherein a plurality of ribs are provided on the surface of the corrugated sheet, the ribs being oriented to the direction coinciding with the direction of ridges of the wave configuration.
A twenty-second embodiment provides a midsole assembly according to the twelfth embodiment, wherein the corrugated sheet is comprised of a first corrugated sheet and a second corrugated sheet, the first corrugated sheet being formed of thermoplastic or thermosetting resin, the circumferential end surface thereof being located inside the side surface of the heel portion of a shoe, the second corrugated sheet being formed of soft elastic material having smaller modulus of elasticity than that of the first corrugated sheet, the circumferential end surface thereof being located at substantially the same position as the side surface of the heel portion of a shoe.
In a twenty-third embodiment, there is provided a process for forming a midsole assembly for an athletic shoe wherein a corrugated sheet is disposed in at least a heel portion of a midsole. In this embodiment, the process comprises the steps of overlaying a first flat sheet on a second flat sheet, where the first flat sheet is formed of thermoplastic or thermosetting resin and the circumferential end surface thereof is located inside the side surface of the heel portion of a shoe, and the second flat sheet is formed of soft elastic material having smaller modulus of elasticity than that of the first flat sheet and the circumferential end surface thereof is located at substantially the same position as the side surface of the heel portion; and forming the first and second flat sheets into corrugated sheets by placing the first and second flat sheets in a mold and thermoforming them.
For a better understanding of these and other embodiments of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.